Process of intimately mixing sulphuric acid and lubricating oil stock



March 9, 1937. PFAU ET A 2,073,253

PROCESS OF INTIMATELY MIXING SULPHURIC ACID AND LUBRICATINQG OIL STOCK Filed Aug. 9, 1952 3 sheets-sheet 1 AGITATORS INVENTORS C-l eo rye M P162 a Z 32 March 9, "1937. ca. M. PFAU ET AL I 2,073,253

PROCESS OF INTIMATELY MIXING SULPHURIG ACID AND LUBRICATING OIL STOCK Filed Aug. 9, 1952 3 Sheets-Sheet 2 Q I w I w w I 2% m i= George/W. ffa a 11v VENTORS March 9, G M PFAU ET AL PROCESS OF INTIMATELY MIXING SULPHURIC ACID AND LUBRICATING OIL STOCK Filed Aug. 9, 1952 3 Sheets-Sheet 3 A6 I TATO R5 AG H'ATOQ l/V V/f/V TOMS I George M. Pfau Dayfon 61.502171 ErnesW Zub/i/Z Patented Mar. 9, 1937 UNITED STATES PROCESS OF INTIMATELY MIXING SUL- PHURIC ACID AND LUBRICATING OIL STOCK George M. Pfau, Dayton 0. Bolin, and Ernest W. Zublin, Fort Worth, Tex, assignors to Texas Pacific Coal & Oil 00., Fort Worth, Tex., a corporation of Texas Application August 9,

9 Claims.

This invention relates to the sulphuric acid treatment of lubricating oil stocks, and more particularly to a method for the treatment of the oil in a continuous manner with a definitely regulated amount of acid.

Heretofore, heavy lubricating oil stocks which normally have a viscosity of '70 to 160 Saybolt universal seconds at 210 F. and higher have been treated for the removal of asphalt and tarry matters and for improvement in color with varying quantities of sulphuric acid by batch or intermittent methods. The batch process has several severe disadvantages, some of which are over-treatment of part of the oil and insufficient treatment of the balance; difiicult control of time of contacting and mixing; slow separation of acid oil and sludge; partial hydrolysis of the products of treatment by the necessary addition of water for coagulation of the acid particles; and extremely high losses of oil in the sludge. The intermittent or batch method also requires large and bulky equipment, long pipe lines, and has numerous fittings exposed to rapid corrosion and long operating cycles extending from 18 to 36 hours.

It is known that light dewaxed distillates have been treated in a diluted condition in a continuous process, but such treatment is not adaptable to heavy lubricating or cylinder stocks in the undiluted state. Treating in dilution is dangerous due to the large amount of highly volatile naphtha employed in the operation and the large equipment necessary to take care of the additional volume of liquid, equal to from to 55% of the stock to be treated, and finally there is a considerable loss of the solvent.

It is also known that attempts have heretofore been made to continuously treat heavy lubricating stocks with sulphuric acid. These attempts have not met with satisfactory success for the reason that the mechanical equipment employed in the treatment have not been capable of maintaining a correct measurement of the quantity of acid mixed with theregulated quantity of oil over any extended period of time. The acid lines and measuring equipment sooner or later become corroded causing fluctuation in the acid flow and consequent under-treatment or over-treatment and unnecessary waste of acid.

It is one of the objects of the present invention to continuously and uniformly treat lubricating oil stock with sulphuric acid to bring out a better and more uniform color and purification in the finished product, with smaller losses, shorter operating cycles and higher yields of refined oil.

Another object of our invention is to provide a continuous treatment for lubricating oil stocks in which there is a uniform, uninterrupted, and non-pulsating flow of acid entering into the mixture with the oil, and in which the mixing of the 1932, Serial No. 628,064

viscous oil and acid may be more carefully controlled in quantity, and in the necessary time of contact.

Further objects and advantages of our invention will appear from the following description thereof taken in connection with the attached drawings which illustrate preferred embodiments of our apparatus.

In accordance with the present invention, a uniform flow of acid or other corrosive liquid is obtained by continuously flowing the liquid at a uniform temperature from a source of supply to a tank in which a constant level of liquid is maintained through control of the inlet speed, and by gravity discharging the liquid from the tank out of a pipe connected thereto having at its discharge end a tip composed of a non-corrosive material such as glass or agate through which the liquid passes and which because of its noncorrosive and abrasion-resisting qualities will not change in area over exceedingly long periods of time.

The continuous treatment of oil with acid, in accordance with this invention is obtained by mixing the constant'and uniform stream of acid obtained as above described with a regulated stream of oil in proper proportions and passing the mixture through a continuous agitator and through one or more centrifugal machines of standard construction.

Uniformity in the acid treatment of the oil and more eificient action of the acid, constituting a further feature of the invention is obtained by thoroughly contacting all parts of the oil with acid for a definitely controlled period of time. This contact is effected by combining forced feed of oil and acid with intensive agitation and with a shearing action, said action being obtained by passing the oil-acid mixture between relatively moving surfaces in such a manner that the mixture is smeared over the surfaces to expose greater areas of each substance to the other, all as will hereinafter be more fully explained.

Another feature of the present invention is the discovery that the treatment of the oil with the acid in two stages instead of one provides a process having additional unexpected advantages including a higher yield of purified oil, a more thorough purification and decolorization and a less consumption of acid.

In this two stage embodiment of the invention, the acid and oil are mixed in measured quantities as hereinbefore described, the amount of acid, however, being in a somewhat smaller proportion. The mixed oil and acid is then passed to an agitator in which a medium degree of agitation of short duration is effected. After agi tation, the sludge is quickly separated from the treated oil as by centrifuging. The partially purified oil obtained is then mixed with an additional but smaller quantity of acid suitably measured in the same manner as hereinbefore described and is then violently agitated for a longer period of time and finally is separated as by centrifuging.

The agitation in the initial treatment may be satisfactorily carried out in a single unit or chamber of the agitation apparatus of the present invention and the agitation in the second treatment in a plurality of the chambers in series. The number of chambers employed and the speed of rotation of the paddle in the two stages obviously must be varied with the kind and quality of the oil being treated. Obviously, also the total quantity of acid and the amount used in each stage is dependent'upon the nature of the oil being treated.

In the drawings:

Figure l is a schematic diagram of the oil treating apparatus;

Figure 2 is a vertical cross section through one form of flow regulating device in the acid pply p p Figure 3 is a side elevation of a multiple series agitator with parts broken away and parts in section to show the internal construction;

Figure 4 is a transverse section taken substantially on the line 44 of Figure 3, showing the rotatable disc;

Figure 5 is a transverse section taken particularly on the line 55 of Figure 3, showing the fixed baffle;

Figure 6 is an end elevation of the paddle, and,

Figure 7 is a second modification of the oil treating apparatus illustrating a two-stage treatment of the oil with acid.

The continuous treatment of lubricating oils witl sulphuric acid involves a very complete mixing of the oil and the acid in order to insure a complete treatment of all of the oil without parts being undertreated or other parts being overtreated. For continuous treatment, the acid supply must be accurately proportioned at all times to the amount of oil to prevent improper treatment, of the oil or waste of acid. One form of apparatus which will secure these results is shown in the schematic layout in Figure 1. The diagram, however; is merely illustrative of the preferred steps of the process and of the preferred form of apparatus.

The, oil supply is contained in a reservoir in and the acid in a suitable reservoir 12. The acid is conducted through a suitable conduit M into an intermediate or control tank H5, in which the flow is regulated by the float l8 controlling the valve 223. With such an apparatus it will be obvious that a constant level of acid may be maintained in the intermediate tank l6 at all times.

The acid in this embodiment is siphoned out of the tank 16 by means of a conduit 21 composed wholly of a hard, non-corrosive material such as glass. The siphon 2'! is started by applying a vacuum to the pipe 23 connected to the acid trap 24 which through the intermediate connection 25 will withdraw any air in the siphon 2| in a well known manner. The valve 26 will break the vacuum if desired. From the siphon 2!, the acid falls into an enlarged end of pipe 28.

With the construction described a constant level of acid will be maintained in the compartment I6 and there will thus be a uniform flow of acid to the lower end of the pipe 2|. So long as the opening in the end of this pipe remains a constant size, the flow of acid therefrom will always remain uniform.

It is essential in maintaining a uniform flow over long periods of time that the opening in the discharge pipe does not become worn and enlarged. For this reason the pipe 2| is made of abrasion resisting material such as glass, which material is not subject to corrosion with either dilute or concentrated sulphuric acid. The area of the opening will remain the same for an indefinite period. There will thus be a uniform flow to the control means 29. The amount of acid delivered may be regulated by varying the level of acid in the tank l6. A gauge I9 is provided and is, if desired, calibrated to read pounds per hour of liquid fed. The gauge facilitates accurate control,

The oil from the reservoir I0 passes into the oil flow control and out in a uniform measured amount. The mixed oil and acid flow into the agitator 30, in the proper proportions and at the proper rate for the agitator.

The multiple agitator 30 is more clearly shown in Figure 3, and it is made up of separate units 30a, 3| and 32, the units 33a and 32 being re spectively provided with an intake pipe 33 and a discharge pipe 34. The intermediate units 3| are similar in size and shape, all of the units being preferably bolted together to form a single machine.

The multiple agitator is preferably cylindrical in form. The compartments or units are sepa rated by baflle plates 35-. As more particularly shown in Figure 5, each baflle plate 35 has a plu rality of holes 36 through which the oil and acid is forced. Mounted immediately against each bafile plate, there is a rotatable disk 37 having vane type slots 38 which cooperate with the apertures 36 to conduct the oil and acid from substantially at the center to the periphery of the container. These disks serve to force the oil and acid into further intimate admixture by subjecting thetwo to a shearing action between the disks and; the fixed baflle plates 35. As the oil is forced through the holes it is carried along the surface of the disks until it finally works out at the periphery.

Each compartment has a rotatable paddle 39 carried on the central driving shaft 40 which is conveniently rotated by the pulley 4|. Suitable packing boxes 43 may also be used on the ends of the agitator to seal the compartments against leakage. The rotatable agitating means 39 pref erably has two blades 42, which are of a curved ribbon shape. The interior of the compartment 32 is illustrated as though the casing were merely broken away, thus showing both ends of. the paddle. The compartment 3| is illustrated by a central section through the blades 42 which are thus shown broken at the center line. The construction of the hub of the agitating means 39. and blades 42 is more clearly shown in Figure 6. The blades extend substantially throughout the longitudinal length of the chamber of the respective units of the agitator and substantially in contact with the interior surface thereof to exert a conveying or pumping action on the liquid introduced therein. It will thus be seen that the oil-acid mixture entering the multipl agitator through the pipe 33 is progressively forced through each of the units and through each of the fixed baflle plates 35, and is periodically sheared by the rotating disks mounted between the compartments. In this manner the oil and acid become completely mixed. The mixture then passes out through the discharge pipe 34. Since the oil and acid continuously enter the pipe 33 and continuously pass out through the pipe 34 a continuous agitation is effected. With this type of agitation it is thought impossible that any oil could get out of the container without a very intimate contact with acid. This intimate mixing and forced feed prevents the overtreatment of one part of the oil and the undertreatment of any other part.

After the oil and acid have been completely intermixed they are passed into a suitable centrifuge 44 in which the sludge is separated from the treated oil. The sludge passes out the lower pipes 45 of the centrifuge, while the oil passes out of the higher tube 45, and is conveyed to suitable tanks for further treatment. The tube 41 is an overflow.

Figure 2 illustrates an alternative type of outlet from the tank l6 which, instead of being a siphon tube composed wholly of glass or the like is connected to the bottom of the tank and is constructed of a corrosion resisting metal having a tip 21 of a hard non-corrosive material, such for example, agate. Unlike the so-called noncorrosive metals which corrode under the action of acid and moisture from the atmosphere, the agate will not in the least be aifected. Consequently the provision of an agate tip eliminates fluctuations in the acid stream heretofore resulting from the use of discharge pipes constructed totally of metal.

As a specific example, the following figures are given to show the value of the described process and equipment using 40 pounds of 98% sulphuric acid per barrel of lubricating stock having a viscosity of Saybolt universal seconds at 210 F. and produced from Ranger crude as follows:

(a) Of a construction heretofore used in attempts at continuous treatment.

(b) Constructed in accordance with the present invention.

* Used for neutralization of the acidulated oil,

Test No. 2

Continuous Batch treatment treatment multiple agitator Nature of stock Ranger Ranger Saybolt Univ. vis. at 210 F 9O 9O Treating temp. F 110 Pounds 98 percent sulphuric acid per bbl 40 20 Percent clay by weight* 10 10 Color of finished oil, Tag-Robinson colorimeter 2% 2% Used for neutralization of the acidulated oil.

From Table No. 1 it will be noticed that the use of the same amount of acid in each test produces with the multiple agitator a decidedly better color than is obtained with the batch process or with the single agitator process.

It Will be noticed in Table No. 2 that the amount of acid required to produce a certain color in the finished lubricating oil in the continuous treatment using the multiple agitator is just one-half of that required in the batch process and in the continuous treatment using the heretofore known form of single agitator. The cost of acid and of equipment for the treatment of an equal amount of heavy lubricating stock is thus cut in half by our invention, and furthermore, the loss incurred by the formation of heavy sludge-s, which serve no useful purpose and cause heavy expense for their removal, is also reduced to approximately one-half.

Inasmuch as different oils may require a more or a less extensive period or degree of mixing, it is made possible to add other units to the agitator, and to remove units already attached. The shaft 40 permits the addition and the removal of units without difficulty. The apparatus may be made of any suitable diameter to handle either small or large quantities, and if desired and conditions warrant, a plurality of agitators may be placed in parallel connection so that one or more may be used simultaneously and in case of operating difiiculty one may be turned off and another one connected into the line to take its place without interrupting the continuous flow of oil and acid.

Since the present invention relates to processes, it is obvious that the apparatus may be modified in certain respects without causing a departure from the process invention. Therefore the specific apparatus for obtaining constant acid control and for obtaining the multiple series agitation are not essential to the success of the process, although they bring about desirable operating results. We therefore desire a broad interpretation of our invention within the scope and spirit of the disclosure herein and of the claims appended hereinafter.

Referring more in detail to Figure 7, there is diagrammatically illustrated a further embodiment of the invention in which the oil is treated in a continuous manner with acid in two stages instead of in one.

In the initial stage, acid in the tank IZa passes from the control tank lBa in a smaller amount than in the single-stage treatment, mixes with the oil flowing from tank I Do, and passes through the oil control unit 29a, through a single agitating unit 30a to the usual centrifuge 44a. The separated oil passing out of the centrifuge outlet 46a,'falls into the intermediate storage tank 122; from whence it passes together with a smaller quantity of acid introduced from tanks E211 and 16b, to the oil control 2% and to the multiple stage agitator 30b. constructed in the manner hereinbefore described. After this agitation the retreated oil is centrifuged in 44b, the purified oil passing from outlet 46b and the sludge from outlet 45b.

As an example of the two-stage treatment, a lubricating oil such as a paraffin base residual oil of 80 to Saybolt viscosity at 210 F. is mixed with acid, such as 98% sulphuric acid, in the proportion of from about 10 to 18 pounds of acid per barrel of oil. A quantity of acid which will produce an oil after a standard clay treatment having a color of about one in the Tag- Robinson colorimeter has proven very satisfactory.

The treated oil obtained after the first centrifugation is mixed with suitably about 5 pounds of similar acid and the mixture passed through a multiple agitator having four units. The quantity of acid used and the time and intensity ofagitation employed are regulated to prevent the appearance of free acid in the sludge discharged from the centrifuge. The retreated oil after a standard clay treatment has a color in the Tag- Robinson colorimeter of about 4 to 5.

Obviously the details of practice of the processes of the present invention must be determined for each particular oil treated.

We claim:

1. The process of purifying heavy lubricating oils with concentrated sulphuric acid which comprises, siphoning a stream of acid from a body of. the liquid maintained at a constant level, and discharging a uniform flow stream from the siphon at a fixed level through a non-corroding orifice of fixed size, combining said stream with a uniformly flowing stream of oil, agitating the mixture in a closed compartment from which air is excluded, localizing the mixture and subjecting the same to a shearing action wherein the same is smeared between closely positioned relatively moving surfaces to expose large areas of contact for further intimate mixing of the oil and acid, and centrifugally separating the oil from the sludge formed.

2. The process of intimately mixing sulphuric acid and lubricating oil stock to obtain intimatecontact between the same which comprises the steps of constantly introducing the oil and the acid together in uniform amounts intoan agitating zone, and subsequently mixing said oil and acid by subjecting them to agitation and to a shearing action between closely positioned. relatively moving surfaces, wherein the oil and acid are smeared upon said surfaces to present comparatively large areas of contact therebetween.

3. The process of continuously mixing acid and oil in a multiple agitator to obtain intimate contact between the same which comprises repeatedly agitating the mix in sequential steps, and shearing the mix between closely positioned relatively moving surfaces, whereby the oil. and acid are smeared upon said surfaces to present comparatively large areas of contact therebetween.

4. The process of decolorizing oil which comprises the steps of continuously supplying} a regulated volume of acid. to said oil, agitating said acid and oil in a closed compartment, passing said oil and acid mixture between closely positioned relatively moving shearing surfaces whereby the oil and acid are smeared upon said surfaces to present comparatively large areas 60 acid to obtain intimate contact between the same comprising establishing constant and uniform-- streams of acid and of oil, mixing said streams,

subjecting said mixture to agitation and to a shearing action between surfaces wherein the oil and acid are smeared upon said surfaces and caused to present relatively large areas of contact to each other and centrifuging, thereby separating the treated oil from the sludge formed.

6. The process of continuously treating oil.-

with acid to obtain intimate contact between the same comprising establishing constant and uniform streams of acid and of oil, mixing said streams, and flowing said mixture at a uniform rate through an agitating means, periodically subjecting said flowing mixture to a shearing action between closely positioned relatively moving surfaces wherein the oil and acid are smeareduponwith acid to obtain intimate contact between the same comprising establishing constant and uniform streams of acid and of. oil, mixing said streams, agitating said mixture in av series of steps, forcing said mixture during agitation through the agitating means and between closely positioned relatively moving andrelatively large area shearing surfaces interposed between each stage whereby said oil is smeared upon said surfaces and caused to uniformly contact with said acid over a relatively large area, and centrifugally separating the treated oil from the acid sludge.

8. The process of continuously treating lubricating oil with acid to obtain intimate contact between the same comprising establishing constant and uniform streams of acid and of oil, mixing said streams, uniformly agitating. said mixture by continuously passing the same through an agitator under forced feed and between shearing surfaces wherein the oil and acid are smeared over said surfaces to present large areas for intimate contact therebetween, and quickly separating the treated oil from the sludge formed.

9. The process of continuously treating lubricating oil with acid to obtain intimate contact, between the same which comprises establish ing constant and uniform streams of acid'and of oil, mixing said streams, uniformly agitating said mixture by continuously passing the same through an agitator under forced feed and between shearing surfaces wherein the oil and acid are smeared over the surfaces topresent large areas for intimate contact therebetween, repeating the agitation and shearing action and quickly separating the treated oil from. the sludge formed.

GEO. M. PFAU. DAYTON C. BOLIN. ERNEST W. ZUBLIN. 

